HP has rarely been afraid to copy good design. The company's Envy laptops have long resembled Apple's MacBooks, and last year many of the company's mid-range touchscreen machines adopted the detachable Asus Transformer style. Today, HP is announcing a computer cut from a slightly different cloth: the new HP Pavilion x360 is clearly inspired by Lenovo's successful Yoga lineup of backflipping convertible PCs. Like the Yoga, the x360 lid is on a hinge that rotates all the way around the machine, so you can hold it flat against the back like a tablet, or prop it up in "tent" or "stand" modes when there's a flat surface within reach. And just like Lenovo's most recent addition to the lineup, the Yoga 2 11, the computer runs Windows 8.1 on an I...